It was "the budget", in the 1970s, that first alerted me to the importance of politics. I was fascinated by the intensity with which this great yearly occasion was reported, and the avidity with which my parents and their friends would discuss it – rarely without a great deal of passionate anger. One really didn't know quite what was in the hallowed red box, back then, until the budget speech was delivered.

Whatever posterity will make of this year's effort, it has already gone down in history as the leakiest, most trailed, most pre-announced budget ever.

This, everyone agrees, is down to the Lib Dems, who have been fantastically eager to get across to the public that the progressive bits of the budget are their bits. Much good it will do them. While the Lib Dems certainly didn't invent political leaking, it isn't seen as A Good Thing, and they won't be admired for their loose, eager tongues. The Lib Dems, here, are in a no-win situation, just as they always have been. Their refusal to see they cannot gain from their position is just one long, embarrassing advertisement for their lack of political acumen.

It's a shame really. One could have made much better arguments for this budget being "Lib Dem" than Lib Dem cabinet ministers themselves managed, if only they could master the art of being constructively critical coalition partners rather than being doggedly, almost mechanically, focused on flagging up the parts of the coalition agreement that the Lib Dems have achieved.

Look at pensioners and tax, for example. "Pensioner" is an extremely value-laden word. For me, it conjures a vision of a very frail, old lady, sitting in a kitchen too abject for a John Osborne play, querulously agonising over whether to buy a few tins of cat food or a little coal. Frankly, that's a pretty stupid way of classifying absolutely everyone over 65. In fact, it's discriminatory. It's the sort of thing the Lib Dems should stand against.

Yet the outrage over the changes in tax arrangements for pensioners is partly fuelled by such lazy and cruelly sentimental thinking.

Pensioners, the argument goes, have been paying tax all their lives. Why shouldn't they have a break? Perhaps it's worth offering a counter-argument: pensioners have been using public services all their lives, and are likely to be using them more as they get older, not less. Why should they have a break?

Of course I don't want the very old lady who lives in my head to suffer. I don't want her to be cold, hungry or frightened. But nor do I think it is helpful that the stereotype of what it is to be a pensioner yells so loudly of victimhood. One minute older people are complaining about prejudice against them, shaking their heads at the "cult of youth", and expressing their horror that wise, experienced and robust people are "being thrown on the scrapheap at 50". The next they are playing up to the idea that 15 years on, one has lived so long and is so worn out that it's fiendish to imagine they should be expected to hand over a bit of their cruise money to the treasury.

Curiously though, while the Lib Dems seem happy enough to leave this one to the Conservatives, the idea of taxing pensions is liberal to the core. Pension income is unearned income. What's more, it is unearned income off investments that came with a hefty tax-break in the first place. The idea someone working full-time should have to get a pay-day loan at the end of the month to feed their families, while paying their income tax, while an affluent and glamorous 70-year-old can play the "poor vulnerable me" card when it suits her, is pretty absurd.

It's especially absurd when so many of these poor old folk are the baby boomers who got free higher education, pre-inflation houses and all the breaks from the previous Conservative administration and the New Labour administration that created such a gap between the rich and poor, and between the young and old today. Pensioners, like everyone else, live in a society riven with inequality, and are sometimes extremely comfortably off indeed.

That's not the only Conservative aspect of the budget that could be argued as Lib Dem. The latter's insistence on raising the tax threshold certainly emboldened Osborne in targeting family tax credits. But actually, they were never a good idea. They subsidise the employers who pay poor wages, but compel the recipients of these wages to apply for the subsidy instead. Their existence is a baleful reminder than the minimum wage is by no means a living wage. Labour is in no position to make that argument, having trumpeted tax credits as a flapship innovation for so many years. The Lib Dems ought to be making such arguments, rather than banging on endlessly about their tax threshold ambitions being almost realised. That's a good policy, but a small part of the overall picture. You'd think, from the way the Lib Dems go on, that it was a panacea.

There is much Labour is hobbled against being too critical of, even in opposition. Labour may jeer at the coalition for dropping the higher rate of tax to 45%, but that's still higher than it was for nearly all of Labour's administration, until the financial crisis prompted the 50p rate's temporary introduction. Why did Labour stand by for a decade, as the rich got richer, leaving the rate at 40p if they do not believe themselves that there is indeed a point at which tax rates become counterproductive?

The Lib Dems are supposed to believe there are smarter ways of taxing the rich. Yet Osborne's plan to put stamp duty at 15% for houses bought through companies is much smarter than Vince Cable's mansion tax. One rather hopes that very many more wheezes like this one, which offers lower tax rates as a carrot, and higher tax rates as a stick, are being dreamt up right now in the corridors of Whitehall.

Actually, this budget was interesting. There's no reason to doubt that Lib Dem influence helped to make it interesting. But the Conservatives will be in no hurry to let them claim all the credit for any policy that proves popular with voters.

What has been striking about the coalition thus far is how wonderfully useful it has been for its dominant partner. The Lib Dems attract and absorb the bulk of any campaigning attention against unpopular bills, as they do the bulk of the hatred when those bills go though. They themselves bleat truthfully but cravenly that they negotiated some important concessions, but rarely – never – create space to explain what an alternative, Lib Dem-formulated policy would actually look like.

The Lib Dems have got a little wiser since the early days, when they were forever on the stump, disingenuously flogging Conservative policies and looking shocked because no one was thanking them for their trouble. But not much wiser. They are still nakedly thrilled that they got to hang out with the big boys at all. This only serves to emphasise what little boys they are themselves.